1. Field of Invention
This invention relates generally to identification tags and, more particularly, to a system and method for the simultaneous detection of 8.2 MHz EAS tags and 13.56 MHz ISO15693 RFID Tags.
2. Description of Related Art
The use of EAS (electronic article surveillance) tags and RFID (radio frequency identification) tags for a wide variety of read, track and/or detect applications is rapidly expanding. A smooth bridge between existing EAS and RFID functionality has been a consistent theme identified by users interested in RFID to allow them to obtain the benefits of RFID while maintaining their investment in EAS technology and its usefulness in protecting lower cost objects for sale that cannot justify the higher implementation cost of RFID. However, where identification tags are capable of receiving both EAS and RFID frequencies, the conventional manner in which the respective EAS or RFID signals return from these tags is processed exhibits certain shortcomings or limitations. For example, the reader for these signals comprises an 8.2 MHz EAS transceiver and a 13.56 MHz RFID transceiver in the same package that drive separate antennae. The interference between the two technologies is handled by traditional analog signal filtering techniques. Utilizing such a configuration, though, involves: redundancy of components (i.e., duplication of transceiver components, duplication of antennae, etc.); the degree of filtering required is great (estimated at 100 dB) due to the very close proximity in frequency (less than 1 octave) and the relative signal amplitude differences allowable for the 2 transmission bands; the need for 2 antennae results in a much wider structure (roughly double) than for either technology deployed alone; and even with these techniques, performance is inferior than for either technology deployed alone.
Although “pulse-listen” methodologies (e.g., transmitting a sequence of RF burst signals at different frequencies so that at least one of the frequencies bursts falls near a resonant frequency of the identification tag) are related to the present invention, e.g., U.S. Pat. No. 6,249,229 (Eckstein, et al.), which is incorporated by reference herein, one of the disadvantages of these is that when RFID tags are used, there must be a continuous signal emission from the reader to power the RFID chip.
Communication with RFID tags can include two modes of operation: “tag talk first” (TTF) or “reader talk first” (RTF). In TTF mode, the tag transmits its information upon receipt of the reader's signal. In contrast, in RTF mode, the reader emits commands to the tag (to avoid collisions) and the tag emits responses to those commands. Thus, RTF is the more complex of the two modes and it is RTF operation to which the present invention pertains.
Thus, there remains a need for a system and method that can simultaneously detect EAS and RFID identification tag signals while avoiding the shortcomings discussed previously.